The present invention relates to an automatic transmission provided with an overdrive device of the type in which a torque converter, an automatic transmission and a final reduction gear are integrally assembled, and more particularly relates to an automatic transmission which is directly connected with an engine in the overdrive condition.
In a conventional automatic transmission with an overdrive device, power from the engine crankshaft is transmitted to an overdrive device through a torque converter even in the overdrive condition. In such construction it has been impossible to attain as low a fuel consumption as with a manual transmission, because of transmission loss due to the torque converter in the overdrive condition. Further, planetary gears are generally used for a gear mechanism of the overdrive device, since the power transmission flow is arranged on the axis. Such a construction makes the apparatus large and complicated. Also the apparatus should be provided with at least two pairs of transmission elements, which cause complication of the hydraulic control system.